Veterinary antimicrobials and antiparasitics in fee-fishing ponds: analytical method and occurrence*

ABSTRACT

The aim of this work was to develop and validate a method using online solid-phase extraction and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry to determine residues of 22 veterinary drugs including sulfonamides, amphenicols, fluoroquinolones, benzimidazoles, trimethoprim (TMP) and oxytetracycline (OTC) in water from fee-fishing ponds. The optimal analytical conditions were as follows: XBridge C8 SPE column, Acquity UPLC CSH C18 analytical column, sample loading with water:methanol (98:2, v/v), mobile phase of water with 0.1% acetic acid:methanol (with gradient elution) and eluent flow rate of 0.3 mL min^?1. Quantification was performed in selected reaction monitoring mode and sulfadimethoxine-d₆, ciprofloxacin-d₈, florfenicol-d₃ and albendazole-d₃ were used as internal standards. Water samples collected from 11 fee-fishing ponds showed the presence of residues of FF (0.42–0.74 µg L^?1), albendazole (0.05–0.31 µg L^?1) and thiabendazole (0.45 µg L^?1). Thiamphenicol and TMP were detected at concentrations lower than the limits of quantification of the method (0.1 and 0.001 µg L^?1, respectively).     

Sensitive Simultaneous Determination of o-Nitrophenol and p-Nitrophenol in Water by Surfactant-Mediated Differential Pulse Voltammetry

A simple, low-cost and sensitive electroanalytical method was developed for the simultaneous determination of p-nitrophenol and o-nitrophenol isomers in water samples at a glassy carbon electrode (CGE) in the presence of cationic surfactant. The electrochemical behavior of p-nitrophenol and o-nitrophenol was studied by cyclic voltammetry (CV) in 0.1?mol L^?1 acetate/acetic acid buffer (pH 3.70) in the presence and absence of cetylpyridinium bromide. The resolution of overlapped cathodic peaks potentials (E_pc) of isomers was successfully improved in the presence of 100.0?µmol L^?1 cetylpyridinium bromide, thus making this approach ideal for the simultaneous determination of isomers. Under the optimized conditions in 0.05?mol L^?1 HEPES buffer at pH 7.0 using differential pulse voltammetry (DPV) at a scan rate of 45?mV s^?1, pulse amplitude of 220?mV and modulation time of 10?ms, limits of detection 0.59?µmol L^?1 for p-nitrophenol and 1.14?µmol L^?1 for o-nitrophenol were obtained with linear ranges from 2.0 to 60.0?µmol L^?1 and 3.0 to 60.0?µmol L^?1, respectively. The intraday precision was assessed as relative standard deviation (%) for 20.0 and 40.0?µmol L^?1 concentrations were 4.30% and 2.41% for p-nitrophenol and 4.87% and 2.20% for o-nitrophenol, respectively. The developed method was applied for the determination of the isomers in lake water samples. The accuracy was attested by comparison with high-performance liquid chromatography with diode array detection (HPLC-DAD) as a reference analytical technique. Recovery values ranging from 90.3% to 111.8% also attested to the accuracy of method for analysis of real samples.     

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30?µg?L^?1 and 2.6?µg?L^?1, respectively. A precision expressed as relative standard deviation (RSD, n?=?10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.     

Trace determination of malachite green in water samples using dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography-diode array detection

A simple and reliable method has been developed for the rapid analysis of trace levels of malachite green from water samples using dispersive liquid–liquid microextraction and high-performance liquid chromatography-diode array detection. Factors relevant to the microextraction efficiency, such as the type and volume of extraction solvent, nature and volume of the disperser solvent, the effect of salt, sample solution temperature and the extraction time were investigated and optimised. Under the optimal conditions the linear dynamic range of malachite green was from 0.2 to 100.0?µg?L^?1 with a correlation coefficient of 0.9962. The detection limit and limit of quantification were 0.1?µg?L^?1 and 0.3?µg?L^?1, respectively. The relative standard deviation (RSD) was less than 2.6% (n?=?5) and the recoveries of malachite green (5.0?µg?L^?1) from water samples were in the range of 99.2?±?1.7%. Finally the proposed method was successfully applied for the analysis of malachite green from fish farming water samples.     

Determination of Simazine and Atrazine in River Water by Cloud-Point Extraction and High-Performance Liquid Chromatography

Atrazine and simazine are endocrine-disrupting herbicides that may be transported to surface water, unbalancing ecosystems. Sensitive and low-cost methods are required for monitoring the residues of these compounds. Although several highly sensitive chromatographic methods coupled to tandem mass spectrometry are available, these methods use high-cost instrumentation. Ultraviolet detection usually does not provide the sensitivity and selectivity for monitoring these herbicide residues at the maximum concentrations levels permitted by regulatory agencies, so that extraction and concentration steps are required. Cloud-point extraction in Triton X-114 micelles was investigated to extract and preconcentrate atrazine and simazine. Treatment of 10?mL of sample solutions with 5?mL of 5% (m v^?1) Triton X-114 in the presence of NaCl (0.3?g) with heating at 60°C for 30?min led to phase separation and the transfer of herbicides to the surfactant-rich phase, which was dissolved in 90:10 methanol:water for liquid chromatography analysis with ultraviolet detection. The linear dynamic range was 1–50?µg?L^?1 for the herbicides. The limits of detection were 0.13 and 0.27?µg?L^?1 for simazine and atrazine, respectively. The methodology was applied to water samples fortified with 1, 5, 15, and 50?µg?L^?1 of the analytes, resulting in recoveries between 86 and 132% with relative standard deviations less than 6%. The method is low cost and uses small volumes of toxic solvents with useful application in trial studies.     

1-Butyl-3-methylimidazolium hexafluorophosphate ionic liquid-based liquid–liquid microextraction for the determination of 4-nonylphenol and 4- tert -octylphenol in environmental waters

In the present study, room-temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate was used as extraction solvent in a liquid–liquid microextraction (LLME) procedure followed by liquid chromatography for determining 4-nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP) in environmental water samples. RTIL-based LLME was a simple, inexpensive, and fast sample preparation method, and its parameters such as extraction time, addition of salt, selection of phase ratio, and pH value were optimized. The optimized method had acceptable limits of detection (LOD) and a precision of 2?µg?L^?1 and 8.1% for 4-NP and 0.6?µg?L^?1 and 3.7% for 4-t-OP, respectively. The proposed method was successfully applied in river water and effluent from a sewage-treatment plant, and the recoveries spiked at 6?µg?L^?1 and 25?µg?L^?1 levels were in the range of 82–113%.     

Screen-printed electrodes incorporated in a flow system for the decentralized monitoring of lead,cadmium and copper in natural and wastewater samples

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025?M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8?µg?L^?1, 4.1?µg?L^?1, and 7.5?µg?L^?1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples.     

Sensitive determination of Fenamiphos in water samples by flow injection photoinduced chemiluminescence

In this work, a sensitive flow injection chemiluminescence (FI-CL) method for the determination of nematicide Fenamiphos in a rapid and simple way is proposed. Fenamiphos is first photodegraded in basic medium. These photofragments react with Ce(IV) providing the chemiluminescence signal. To the authors’ knowledge, no chemiluminescence method has been described in the literature for the determination of the nematicide Fenamiphos. All physical and chemical parameters in the flow injection chemiluminescence system were optimized in order to obtain the best sensitivity, selectivity and sample throughput. Before the injection of the sample in the FI-CL system, a preconcentration step with solid phase extraction C18 cartridges was performed. By applying solid phase extraction (SPE) to 250?mL of standard (final volume 10?mL), the linear dynamic range was between 3.4 and 60?µg?L^?1, and the detection limit was 1?µg?L^?1. When SPE was applied to 500?mL of standard (final volume 10?mL), the detection limit was 0.5?µg?L^?1. These detection limits are below the emission limit value established by the Spanish Regulations of the Hydraulic Public Domain for pesticides (50?µg?L^?1) and of the same order as the limit established for total pesticides (0.5?µg?L^?1) at European Directive on the quality of water for human consumption. The sample throughput was 126 hour^?1. Intraday and interday coefficients of variation were below 10% in all cases. No interference was registered in presence of usual concentrations of anions, cations and other organophosphorus pesticides. The method was successfully applied to the analysis of environmental water samples, obtaining recoveries between 96 and 107.5%.     

Release and speciation of uranium in low-ionic-strength groundwaters at an abandoned uranium mine in Val Vedello (Orobic Alp—Italy) by adsorptive cathodic stripping voltammetry

Adsorptive cathodic stripping voltammetry (AdCSV) with HDME and a chloranilic acid ligand was used in the trace analysis of uranyl ions at pH?=?2 in low-ionic-strength groundwaters around mining areas. Upon optimization, the limit of detection around 0.10?µg?L^?1 was found with linearity up to 10?µg?L^?1. In the abandoned mining area of Val Vedello (Orobic Alps, Italy), measured uranium concentrations in water ranged from 0.3?µg?L^?1 above the uranium mineralization levels to 145?µg?L^?1 in groundwaters percolating from mine galleries. Such uranium concentrations are related to natural weathering effects of CO₂ and/or hydrogen carbonate ion on uranium mineralizations under oxic conditions. A marked seasonal dependence was then found, in agreement with literature data on a pre-operational survey dating back to 1980–1981. No significant chemical impact of the abandoned mining activity on groundwater quality could be found. Accordingly, no significant increase in contaminants derived from the heat-burn of explosives, such as chloride and nitrate, in groundwaters from mine galleries was found.     

Rapid and sensitive determination of biphenyl and biphenyl oxide in water samples using dispersive liquid–liquid microextraction followed by gas chromatography

A rapid and sensitive method has been developed for the determination of biphenyl and biphenyl oxide in water samples using dispersive liquid–liquid microextraction followed by gas chromatography. This method involves the use of an appropriate mixture of extraction solvent (8.0?µL tetrachloroethylene) and disperser solvent (1.0?mL acetonitrile) for the formation of cloudy solution in 5.0?mL aqueous sample containing biphenyl and biphenyl oxide. After extraction, phase separation was performed by centrifugation and biphenyl and biphenyl oxide in sedimented phase (5.0?±?0.3?µL) were determined by gas chromatography-flame ionisation (GC-FID) system. Type of extraction and disperser solvents and their volumes, salt effect on the extraction recovery of biphenyl and biphenyl oxide from aqueous solution have been investigated. Under the optimum conditions and without salt addition, the enrichment factors for biphenyl and biphenyl oxide were 819 and 785, while the extraction recovery were 81.9% and 78.5%, respectively. The linear range was (0.125–100?µg L^?1) and limit of detection was (0.015?µg?L^?1) for both analytes. The relative standard deviation (RSD, n?=?4) for 5.0?µg?L^?1 of analytes were 8.4% and 6.7% for biphenyl and biphenyl oxide, respectively. The relative recoveries of biphenyl and biphenyl oxide from sea, river water and refined water (Paksan company) samples at spiking level of 5.0?µg?L^?1 were between 85.0% and 100 %.     

A multi-pumping flow system with on-line photochemical conversion and improved sensitivity for phosphorus fractionation in freshwaters

A flow-based procedure with solenoid micro-pumps was developed for phosphorus fractionation (dissolved organic and inorganic phosphorus) in freshwaters. The spectrophotometric detection was based on the formation of molybdenum blue and the organic species were on-line photo-converted to orthophosphate. The analytical response was linear within 10 and 75?µg?L^?1 with a detection limit of 2.0?µg?L^?1 (99.7% confidence level). Coefficient of variation of 1.8% (50?µg?L^?1 P, n?=?20) and sampling rate of 40 determinations per hour were achieved. Per determination, 160?µg (NH₄)₆Mo₇O₂₄, 10?µg SnCl₂, 640?µg K₂S₂O₈ and 10?mg NaOH were consumed, generating 2.0?mL of waste. Slopes of analytical curves obtained for four different organic phosphorus species agreed with those obtained for orthophosphate, indicating quantitative conversion. The results for freshwater samples agreed with those obtained by the AOAC reference procedure at 95% confidence level. The organic matter did not interfere in the photo-oxidative process. The proposed procedure is a fast and environmentally friendly alternative for the phosphorus fractionation in freshwaters.     

On-line simultaneous pre-concentration procedure for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry

An on-line pre-concentration system for the sequential determination of cadmium and lead in drinking water by using fast sequential flame atomic absorption spectrometry (FS-FAAS) is proposed in this paper. Two minicolums of polyurethane foam loaded with 2-(6-methyl-2-benzothiazolylazo)-orcinol (Me-BTAO) were used as sorptive pre-concentration media for cadmium and lead. The analytical procedure involves the quantitative uptake of both analyte species by on-column chelation with Me-BTAO during sample loading followed by sequential elution of the analytes with 1.0?mol?L^?1 hydrochloric acid and determination by FS-FAAS. The optimisation of the entire analytical procedure was performed using a Box–Behnken multivariate design utilising the sampling flow rate, sample pH and buffer concentration as experimental variables.

The proposed flow-based method featured detection limits (3σ) of 0.08 and 0.51?µg?L^?1 for cadmium and lead, respectively, precision expressed as relative standard deviation (RSD) of 1.63% and 3.87% (n?=?7) for cadmium at the 2.0?µg?L^?1 and 10.0?µg?L^?1 levels, respectively, and RSD of 6.34% and 3.26% (n?=?7) for lead at the 5.0?µg?L^?1 and 30.0?µg?L^?1 levels, respectively. The enrichment factors achieved were 38.6 and 30.0 for cadmium and lead, respectively, using a sample volume of 10.0?mL. The sampling frequency was 45 samples per hour. The accuracy was confirmed by analysis of a certified reference material, namely, SRM 1643d (Trace elements in natural water). The optimised method was applied to the determination of cadmium and lead in drinking water samples collected in Santo Amaro da Purificação City, Bahia, Brazil.     

Determination of Selenium by Single-Drop Microextraction and Diffuse Reflectance Infrared Spectroscopy

A simple and convenient assay based on single-drop microextraction with infrared spectroscopy is reported for the determination of selenium. The extraction conditions were carefully optimized and selenium was preconcentrated through single-drop microextraction in 1,2-dichloroethane containing N-hydroxy-N-phenyl-N′-(o-tolyl) benzimidamide. The method is selective and almost all common ions including molybdenum(VI), chromium(VI), and tungsten(VI) did not interfere with the isolation protocol. The selenite band at 875?±?2?cm^?1, which is assigned to the asymmetric vibrational stretch (υ₃), was used for the quantification of selenium. Low limits of detection and quantification of 2.0 and 6.6?µg?L^?1 demonstrate the sensitivity of the method. Good precision was evaluated by the standard deviation (2.0?µg?L^?1) and relative standard deviation (0.5%) for 8?µg?L^?1 was achieved for 10 measurements. The method was used to analyze human blood, urine, and water for selenium.     

Determination of phosphate in freshwater samples by flow-injection with lucigenin chemiluminescence

Lucigenin chemiluminescence (CL) in conjunction with flow-injection analysis (FIA) is used for the determination of phosphate in freshwater samples. The procedure is based on the formation of molybdophosphoric heteropoly acid (MoP–HPA) by the reaction of phosphate and ammonium molybdate under acidic conditions. CL emission was observed as a result of oxidation of lucigenin in aqueous sodium hydroxide solution in the presence of MoP–HPA. Calibration was linear up to 500?µg?L^?1 (r ^2?=?0.9998; n?=?8), with a detection limit (S/N?=?3) of 0.95?µg?L^?1. An injection throughput of 120 h^?1, and relative standard deviation (RSD; n?=?4) of 1.3–3.2% were achieved in the concentration range studied. An on-line chelating column was used to remove interfering cations. The method was applied to freshwater samples, and the results (51?±?1.0 – 107?±?2.0?µg?L^?1) did not differ significantly from results obtained using a spectrophotometric method (52.5?±?1.0 – 102?±?2.0?µg?L^?1) at 95% confidence level (t-test).     

Enhanced Specificity and Sensitivity for the Determination of Nickel(II) by Square-wave Adsorptive Cathodic Stripping Voltammetry at Disposable Graphene-modified Pencil Graphite Electrodes

Chemical sensors relying on graphene-based materials have been widely used for electrochemical determination of metal ions and have demonstrated excellent signal amplification. This study reports an electrochemically reduced graphene oxide (ERGO)/mercury film (HgF) nanocomposite-modified pencil graphite electrode (PGE) prepared through successive electrochemical reduction of graphene oxide (GO) sheets and an in situ plated HgF. The ERGO-PG-HgFE, in combination with dimethylglyoxime (DMG) and square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV), was evaluated for the determination of Ni²⁺ in tap and natural river water samples. A single-step electrode pre-concentration approach was employed for the in situ Hg-film electroplating, metal-chelate complex formation, and non-electrolytic adsorption at –0.7 V. The current response due to nickel-dimethylglyoxime [Ni(II)-DMG₂] complex reduction was studied as a function of experimental paratmeters including the accumulation potential, accumulation time, rotation speed, frequency and amplitude, and carefully optimized for the determination of Ni²⁺ at low concentration levels (μg?L^?1) in pH 9.4 of 0.1 M NH₃–NH₄Cl buffer. The reduction peak currents were linear with the Ni²⁺ concentration between 2 and 16?μg?L^?1. The limits of detection and quantitation were 0.120?±?0.002?µg?L^?1 and 0.401?±?0.007?µg?L^?1 respectively, for the determination of Ni²⁺ at an accumulation time of 120?s. The ERGO-PG-HgFE further demonstrated a highly selective stripping response toward Ni²⁺ determination compared to Co²⁺. The electrode was found to be sufficiently sensitive to determine metal ions in water samples at 0.1?µg?L^?1, well below the World Health Organization standards.     

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

Square wave voltammetric determination of diafenthiuron and its application to water,soil and insecticide formulation

A square wave cathodic stripping voltammetric (SWCSV) method has been developed for the determination of insecticide diafenthiuron. The procedure is based on controlled accumulation of the insecticide on a static hanging mercury drop electrode (SHMDE) at 0.00?mV (vs. Ag/AgCl) in Britton-Robinson buffer solution (pH 7.0). The insoluble mercury compound was reduced at ?510?mV during the cathodic potential scan. The peak currents were linearly related to insecticide concentration between 30.4 and 3200?µg?L^?1 . The detection and quantification limit were 9.1?µg?L^?1 and 30.4?µg?L^?1, respectively. The proposed analytical procedure was applied to natural water and soil samples. The method was extended to direct determination of diafenthiuron in insecticide formulation Polo® 50 WP and average content of 50.3?±?1.7 (m/m) at 90% confidence level, in close agreement with the 50.0% quoted by the manufacturer. HPLC comparison method indicated that accuracy was in agreement with that obtained by the proposed method.     

Highly sensitive ion preconcentration method based on flow sorbent extraction using multiwall carbon nanotubes

In this work a solid phase on-line uranium ion preconcentration system coupled with spectrophotometry has been developed. The method is based on uranyl ion preconcentration at pH 3.75 onto multiwall carbon nanotubes treated with HNO₃. After preconcentration, the uranyl ions are eluted with 0.32?mol?L^?1HCl followed by reaction with 3,6-bis[(2-arsonophenyl)-azo]-4,5-dihydroxy-2,7-naphthalendisulfonic acid 0.08%[w/v] (Arsenazo III), which had maximum monitored absorbance of 650?nm. Effects of the pertinent experimental parameters on the system were investigated by means of 2^6?2 fractional factorial design, while optimization was carried out using the Doehlert matrix. Under optimized conditions, detection and quantification limits were found to be 0.21 and 0.7?µg?L^?1, respectively. The analytical curve ranged from 5 to 150?µg?L^?1 (r?=?0.998), while the relative standard deviations (RSD) were 3.27 and 2.56% for the respective uranium concentrations of 10 and 100?µg?L^?1 (n?=?10). The features obtained for the on-line preconcentration system were: preconcentration factor of 228, concentration efficiency of 57?min^?1, consumption index of 0.13?mL and sample throughput of 15?h^?1. In order to assess the accuracy of the proposed method, addition and recovery studies were carried out on spring water samples from different sources and synthetic seawater with satisfactory results ranging from 94.85 up to 103.65%.     

Ligandless-ultrasound-assisted emulsification microextraction followed by inductively coupled plasma-optical emission spectrometry for simultaneous determination of heavy metals in water samples

In this study, a simple and efficient method of ligandless-ultrasound-assisted emulsification microextraction (LL-USAEME) followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) has been developed for simultaneous extraction, preconcentration and determination of manganese, cadmium, cobalt and nickel in water samples. In the proposed approach, tetrachloroethylene was selected as extraction solvent. The effect of important experimental factors such as volume of extraction solvent, pH, sonication time, salt concentration, and temperature was investigated by using a fractional factorial design (2^5?1) to identify important factors and their interactions. In the next step, a Box-Behnken design (BBD) was applied for optimisation of significant factors. The obtained optimal conditions were: 30?µL for extraction solvent, 12 for pH, 5?min for sonication time, and 5% w/v for salt concentration. The limits of detections (LODs) for Cd(II), Co(II), Mn(II) and Ni(II) were 0.20, 0.13, 0.21 and 0.28?µg?L^?1, respectively. Relative standard deviations (RSD, C?=?200.0?µg?L^?1, n?=?9) were between 3.4–7.5% and the calibration graphs were linear in the range of 0.25 to 1000.0?µg?L^?1 for Mn, 0.5–1000.0?µg?L^?1 for Co and Ni and 1.0–250.0?µg?L^?1 for Cd. The determination coefficients (R ²) of the calibration curves for the analytes were in the range of 0.993 to 0.999. The proposed method was validated by using two certified reference materials, and also the method was applied successfully for the determination of heavy metals in different real water samples.     

Development of solid-phase extraction method for the determination of aromatic sensitisers in paper mill effluent

In this paper, a procedure for the determination of 11 aromatic hydrocarbon-type sensitisers and their related compounds from water samples, used in the manufacture of thermal paper, is presented. The compounds were extracted using a solid-phase extraction (SPE) cartridge with an octadecyl (C18) or a phenyl-bonded silica (PH) sorbent and then determined by gas chromatography–mass spectrometry (GC–MS). Factors affecting the performance of the extraction steps were thoroughly evaluated, and their effects on the yield of the sample preparation were discussed. Under optimised experimental conditions, SPE cartridges were conditioned with 10?mL hexane followed subsequently by 10?mL methanol, loaded with water sample at 2?mL?min^?1, and eluted with 10?mL hexane at 1.5?mL?min^?1. The limits of detection and quantification, calculated for signal-to-noise ratios of 3 and 10, were in the range of 1–5?µg?L^–1 and 2.5–10?µg?L^–1, respectively. Recovery yields of the present method using river water were in the range of 88%–112% with a C18 sorbent and 86%–116% with a PH sorbent. The repeatability, expressed as a relative standard deviation, was in the range of 2.8%–11% with a C18 sorbent and 0.7%–9.7% with a PH sorbent (n?=?4). Analysis of paper mill effluents revealed the presence of aromatic hydrocarbon-type sensitisers with maximum concentrations of up to 5.2?µg?L^?1.